Magnetic field driven nodal topological superconductivity in monolayer transition metal dichalcogenides

Abstract

Recently, Ising superconductors that possess in-plane upper critical fields Hc2 much larger than the Pauli limit field are under intense experimental study. Many monolayer or few layer transition metal dichalcogenides are shown to be Ising superconductors. Here we show that in a wide range of experimentally accessible regimes where the in-plane magnetic field is higher than the Pauli limit field but lower than Hc2, a 2H-structure monolayer NbSe2 or similarly TaS2 becomes a nodal topological superconductor. The bulk nodal points appear on the Γ−M lines of the Brillouin zone where the Ising SOC vanishes. The nodal points are connected by Majorana flat bands, and the flat bands are associated with a large number of Majorana zero energy edge modes that induce spin-triplet Cooper pairs. This work demonstrates an experimentally feasible way to realize Majorana fermions in nodal topological superconductor, without any fine-tuning of experimental parameters.